Mercuric Chloride by Phosphorous Acid. 361 



talline form, probably has a lower vapor pressure than the 

 ordinary amorphous form. Great care must also be exercised 

 in cracking off the top of the test tube, as the latter if not uni- 

 formly handled during the constriction and sealing is apt to 

 splinter. 



It was found advisable in filtering the mercurous chloride to 

 use light suction at first to avoid clogging of the asbestos mat, 

 which would vitiate the experiment because of the delay in 

 stopping the reaction. After practice it was found possible to 

 accomplish the separation of the precipitate from the solution 

 in about one minute (exclusive of washing). In the experi- 

 ments at 60° this time factor is of course of importance. 



Experimental Results. 

 The catalytic effect of hydrochloric acid in the reduction of 

 mercuric chloride by phosphorous acid at 60° is shown in the 

 graph on the following page and at 25° opposite p. 365. The 

 weights of mercurous chloride, five milligrams to the milli- 

 meter, are expressed as ordinates ; and the time, two minutes 

 to the millimeter in fig. I, and one hour to the millimeter in 



fig. II, are expressed as 



s abscissas. 















Table III. 











HgCl 2 



H 3 P0 3 



= 0-132 

 = 0-0575 



gram mols per 



a a a 



litei 



r = a 

 = b 



T 



= 60° 



HC1 



= 0-264 



a a it 



a 



= C 







t 



in min. 



X ■ 



= HgCl 



in mols 





Kx* 







in grams 



K a f 



24 



0-1462 



0-03104 





0-406 





0-189 



59 



0-2880 



0-06115 





0-453 





0-188 



93 



0-3750 



0-07962 





0-510 





0-189 



152 



0-4578 



09720 





0-616 





0-189 



186 



0-4848 



0-10293 





0-684 





0-190 



228 



0-5068 



0-10760 





0-778 





0-191 



GC 



0-5417 



0-1:500 











* Calculated from Equation (6). f Calculated from 



Equation (11), 



HgCl, 



H 3 P0 3 



= 0-132 

 = 0-0575 



gram mols per 



tt a a 



litei 



a 



• = a 



= b 



T 



= 60° 



HC1 



= 0-132 



a tt a 



a 



= C 







t 



in min. 



X : 



= HgCl 











in grams 



in mols 





K,* 





K 2 f 



27 



0-0964 



0-02047 





0-419 





0-200 



59 



0-1928 



0-04094 





0-443 





0-200 



154 



0-3820 



0-08110 





0-557 





0-206 



274 



0-4848 



0-10293 





0-758 





0-214 



360 



0-5132 



0-10896 





0-893 





0-214 



oc 



0-5417 



0-11500 











* Calculated from Equation (6). f Calculated from Equation (11). 



